In the prior art, there has been known a machine tool which makes a rotary tool rotate to cut or otherwise machine a workpiece. Further, there has been known a numerical control machine tool which designates a tool path of a rotary tool in such a machine tool by coordinates of predetermined axes etc. so as to make the rotary tool automatically move while performing machining.
Japanese Patent Publication No. 60-141446A (PLT 1) discloses a rotary tool holder which makes a rotating tool revolve about a center of rotation of a spindle while cutting. This rotary tool holder makes a tool rotate while the tool is accelerated by a planetary gear mechanism. The center of the tool revolves about the center of rotation of the spindle. By using this rotary tool holder, even if the cutter or other rotary tool becomes worn and the rotary tool changes in diameter, the amount of offset can be adjusted to obtain an accurate width dimension.
Japanese Patent Publication No. 7-230312A (PLT 2) discloses a CNC system which is provided with a numerical control device (CNC) and a programmable machine controller (PMC). This numerical control device stores a machining program in advance. A CNC side movement command means decodes this machining program and generates CNC side axial movement commands in accordance with the content. On the other hand, the programmable machine controller stores a sequence program. A PMC side movement command means sends PMC side axial movement commands contained in the sequence program to the CNC side. The CNC system superposes the CNC side axial movement commands and the PMC side axial movement commands to control movement along the respective axes. This publication discloses that the PMC side movement command means outputs commands for causing reciprocating movement in a predetermined section of the Z-axis and the CNC side movement command means outputs commands for causing monotonous linear movement in parallel with the X-axis.